Money taken from my account without my consent

Capitec deducted money from my main bank account to repay money owed by my secondary account and they did that without my permission.They did even contact me about this, they just did what they wanted with my account. I lodged a complaint with them via email and afterwards they deducted again. It was their system error that made the account to become negative. It makes me very angry that they take my money without my consent, that means they own that account not me and I cannot trust them with my money anymore. I want them to repay my money that they took without my consent even after I lodged a complaint.